DOCS: Add option for line-in

[abelmatser]

Can be used for multiple setups, including edge cases where only a single channel is desired. Cpiped nor parec work in these cases.

[Kriegbaum]

I've run these instructions an can confirm this process works well
I was previously using arecord, which would not clip silence and therefore wouldnt properly display 'idle' or 'playing' status on snapserver

[badaix]

Thanks, I'm just wondering, if there is a simpler way using an alsa stream, it should be superior to any pipe solution.

[Syco54645]

Thanks, I'm just wondering, if there is a simpler way using an alsa stream, it should be superior to any pipe solution.

I have done so in this PR. #1002

[artmg]

Hi @badaix - cleanup - as new PR #1002 went into develop in Jun would you like to close this old one?

[abelmatser]

Alternative solution merged. Closing this.